Airplane Climb Thrust Optimization

ABSTRACT

An example method includes: receiving information indicative of a desired aircraft cruise insertion point comprising achieving a desired cruise altitude for an aircraft within: a predetermined period of time from departure, or within a predetermined distance from departure; receiving information indicative of an estimated weight of the aircraft upon the aircraft reaching the desired cruise altitude; determining a desired airspeed for the aircraft based on the information indicative of the estimated weight of the aircraft; prior to a flight of the aircraft, determining, based on the desired airspeed and the desired aircraft cruise insertion point, a climb trajectory for the aircraft; and during a climb flight phase of the aircraft, varying climb thrust of an engine of the aircraft to follow the climb trajectory and achieve the desired aircraft cruise insertion point.

FIELD

The present disclosure relates generally to airplane climb thrustoptimization. More particularly the present disclosure relates tovarying climb thrust during a climb flight phase of an aircraft toreduce maintenance cost of an aircraft engine, reduce fuel consumption,and reduce flight time.

BACKGROUND

In examples, aircraft are designed to meet performance targets atmaximum takeoff weight including takeoff field length and climb time orclimb distance to a desired aircraft cruise altitude. Operation at lessthan maximum takeoff weight allows for a reduction of both takeoff andclimb thrust from maximum ratings. Reducing takeoff and/or climb thrustfrom maximum ratings may be beneficial to engine life.

Time between engine refurbishments and cost of refurbishment aredirectly related to how an engine is operated. The key drivers are stagelength, engine cycles per year, and how hard the engine is used, i.e.,shaft speeds and core temperatures during takeoff and climb flightphases in addition to adverse environmental factors.

Reducing engine thrust during takeoff and climb flight phases may reduceengine core temperatures. In examples, the highest core temperaturemeasured in an engine is turbine gas temperature, which may be measuredby thermocouples or other temperature sensors in the low pressureturbine nozzle guide vanes. High pressure turbine blades achieve some ofthe highest temperatures in an engine and consequently are typicallydamaged by oxidation/burning and erosion. Allowing for reduced thrustduring takeoff and climb flight phases reduces turbine gas temperature,thus reducing engine damage and extending engine life.

It is with respect to these and other considerations that the disclosuremade herein is presented.

SUMMARY

The present disclosure describes examples that relate to airplane climbthrust optimization.

In one aspect, the present disclosure describes a method. The methodincludes: (i) receiving, at a flight management computer, informationindicative of a desired aircraft cruise insertion point comprisingachieving a desired cruise altitude for an aircraft within: apredetermined period of time from departure, or within a predetermineddistance from departure; (ii) receiving, at the flight managementcomputer, information indicative of an estimated weight of the aircraftupon the aircraft reaching the desired cruise altitude; (iii)determining, by the flight management computer, a desired airspeed forthe aircraft based on the information indicative of the estimated weightof the aircraft; (iv) prior to a flight of the aircraft, determining bythe flight management computer, based on the desired airspeed and thedesired aircraft cruise insertion point, a climb trajectory for theaircraft; and (v) during a climb flight phase of the aircraft, varying,by the flight management computer, climb thrust of an engine of theaircraft to follow the climb trajectory and achieve the desired aircraftcruise insertion point.

In another aspect, the present disclosure describes a non-transitorycomputer readable medium having stored therein instructions that, inresponse to execution by a flight management computer, cause the flightmanagement computer to perform operations. The operations include: (i)receiving information indicative of a desired aircraft cruise insertionpoint comprising achieving a desired cruise altitude for an aircraftwithin: a predetermined period of time from departure, or within apredetermined distance from departure; (ii) receiving informationindicative of an estimated weight of the aircraft upon the aircraftreaching the desired cruise altitude; (iii) determining a desiredairspeed for the aircraft based on the information indicative of theestimated weight of the aircraft; (iv) prior to a flight of theaircraft, determining, based on the desired airspeed and the desiredaircraft cruise insertion point, a climb trajectory for the aircraft;and (v) during a climb flight phase of the aircraft, varying climbthrust of an engine of the aircraft to follow the climb trajectory andachieve the desired aircraft cruise insertion point.

In still another aspect, the present disclosure describes a flightmanagement computer including one or more processors; and data storagestoring thereon instructions, that when executed by the one or moreprocessors, cause the flight management computer to perform operations.The operations include: (i) receiving information indicative of adesired aircraft cruise insertion point comprising achieving a desiredcruise altitude for an aircraft within: a predetermined period of timefrom departure, or within a predetermined distance from departure; (ii)receiving information indicative of an estimated weight of the aircraftupon the aircraft reaching the desired cruise altitude; (iii)determining a desired airspeed for the aircraft based on the informationindicative of the estimated weight of the aircraft; (iv) prior to aflight of the aircraft, determining, based on the desired airspeed andthe desired aircraft cruise insertion point, a climb trajectory for theaircraft; and (v) during a climb flight phase of the aircraft, varyingclimb thrust of an engine of the aircraft to follow the climb trajectoryand achieve the desired aircraft cruise insertion point.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the figures and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and descriptions thereof, will best be understood byreference to the following detailed description of an illustrativeembodiment of the present disclosure when read in conjunction with theaccompanying Figures.

FIG. 1 illustrates rate of climb of an aircraft having maximum takeoffweight compared to a rate of climb of the aircraft at less than maximumtakeoff weight, in accordance with an example implementation.

FIG. 2 illustrates rate of climb of an aircraft using derated thrustlevels and tapering back to a full rated climb thrust level, inaccordance with an example implementation.

FIG. 3 illustrates effect of using climb thrust derates on overallmission of an aircraft, in accordance with an example implementation.

FIG. 4 illustrates a block diagram depicting operations associated withdetermining a climb profile of an aircraft, in accordance with anexample implementation.

FIG. 5 illustrates determination of a desired airspeed for the aircraft,in accordance with an example implementation.

FIG. 6 illustrates forces acting on an aircraft, in accordance with anexample implementation.

FIG. 7 illustrates a plot of a climb trajectory of an aircraft whileimplementing the operations of FIG. 4, in accordance with an exampleimplementation.

FIG. 8 illustrates another block diagram depicting operations associatedwith determining a climb profile of an aircraft, in accordance with anexample implementation.

FIG. 9 illustrates a plot of a climb trajectory of an aircraft whileimplementing the operations of FIG. 8, in accordance with an exampleimplementation.

FIG. 10 illustrates another block diagram depicting operationsassociated with determining a climb profile of an aircraft, inaccordance with an example implementation.

FIG. 11 is a flowchart of a method for varying climb thrust of anaircraft, in accordance with an example implementation.

FIG. 12 is a flowchart of additional operations that may be executed andperformed with the method of FIG. 11, in accordance with an exampleimplementation.

FIG. 13 is a flowchart of additional operations that may be executed andperformed with the method of FIG. 11, in accordance with an exampleimplementation.

FIG. 14 is a flowchart of additional operations that may be executed andperformed with the method of FIG. 11, in accordance with an exampleimplementation.

FIG. 15 is a flowchart of additional operations that may be executed andperformed with the method of FIG. 11, in accordance with an exampleimplementation.

FIG. 16 is a flowchart of additional operations that may be executed andperformed with the method of FIG. 11, in accordance with an exampleimplementation.

FIG. 17 is a block diagram of an example flight management computer ofan aircraft, according to an example implementation.

DETAILED DESCRIPTION

Generally, an aircraft that is fully loaded and thus has maximum takeoffweight (MTOW), may take a longer time and distance to reach a targetcruising altitude compared to a lighter aircraft. As an example, anaircraft at MTOW may take about 25 minutes and a ground distance of 150nautical miles (nm) to climb to a cruising altitude of 31,000 feet (ft).However, if the aircraft has a smaller takeoff weight (TOW) the aircraftmay take about 20 minutes and a ground distance of 121 nm to reach aneven higher cruise altitude of 35,000 ft.

Similarly, an aircraft that is fully loaded and thus has MTOW, may havea smaller rate of climb (RoC) compared to a lighter aircraft. Inexamples, the RoC of an aircraft can be defined as a vertical speed ofan aircraft, or in other words the rate of positive altitude change withrespect to time or distance. The RoC may be in feet per minute (ft/min)or meter per second (m/s). The RoC of an aircraft may be indicated witha vertical speed indicator (VSI) or instantaneous vertical speedindicator (IVSI).

FIG. 1 illustrates RoC of an aircraft having MTOW compared to a RoC ofthe aircraft at less than MTOW, in accordance with an exampleimplementation. Specifically, FIG. 1 depicts a plot 100 having a firstline 102 tracing the RoC of the aircraft at MTOW as the aircraft'saltitude increases while the aircraft is using maximum climb thrust. Asecond line 104 traces the RoC of the aircraft at less than MTOW as theaircraft's altitude increases while the aircraft is using maximum climbthrust. The x-axis of the plot 100 indicates the RoC, whereas the y-axisindicates altitude of the aircraft.

As depicted in FIG. 1, the RoC of the aircraft at MTOW is less than therespective RoC of the aircraft at less than MTOW at a given altitude.Thus, an operator of the aircraft expects and accepts that at when theaircraft is operating at MTOW, the climb time, climb distance, and RoCare lower than the respective climb time, climb distance, and RoC forthe aircraft at less than MTOW. Therefore, the operator of the aircraftmay accept derating climb thrust of the aircraft at less than MTOW.Derating the climb thrust may increase the time that the aircraft takesto get to a desired altitude; however engine temperatures may bereduced, leading to an increased engine life and reduced enginemaintenance cost. Thus, derating the climb thrust to a level that wouldcause an acceptable increase in the time that the aircraft takes to getto the desired altitude may be desirable.

In an example implementation, an operator of an aircraft may be given anoption to derate climb thrust to particular values less than maximumclimb thrust. For instance, assuming that maximum climb thrust is CLB,then the operator may select a first derated climb thrust CLB1 that is10% lower than CLB or select a second derated climb thrust CLB2 that is20% less than CLB. The derated climb thrust may reduce the RoC of theaircraft but may increase the life of the engine.

Further, in examples, the operator may be given options to taper thederated climb thrust CLB1 or CLB2 back to CLB to restore the maximum RoCpossible for a given aircraft takeoff weight. For instance, the operatormay have a first option to taper the climb thrust over a small altituderange such as between an altitude of 10,000 and an altitude of 12,000ft. The first option may be referred to as a quick taper as the taperingoccurs over a small altitude range. The operator may also have a secondoption to taper the climb thrust over a larger altitude range such asbetween an altitude of 10,000 and an altitude of 30,000 ft. The secondoption may be referred to as a slow taper as the tapering occurs over alarge altitude range. In other examples, the operator may be given moretapering altitude range options such as between an altitude of 25,000and an altitude of 35,000 ft, an altitude of 25,000 and an altitude of40,000 ft, an altitude of 30,000 and an altitude of 40,000 ft, amongother possible ranges.

FIG. 2 illustrates RoC of an aircraft using derated thrust levels andtapering back to a full rated climb thrust level, in accordance with anexample implementation. FIG. 2 depicts the lines 102 and 104 in additionto lines representing different climb thrust tapering options.

Particularly, line 106 represents using CLB1 (e.g., 10% climb thrustderate) and a quick tapering option (e.g., tapering over altitude range10,000 ft-12,000 ft). Line 108 represents using CLB1 and a slow taperingoption (e.g., tapering over altitude range 10,000 ft-30,000 ft). Line110 represents using CLB2 (e.g., 20% climb thrust derate) and a quicktapering option (e.g., tapering over altitude range 10,000 ft-12,000ft). Line 112 represents using CLB2 and a slow tapering option (e.g.,tapering over altitude range 10,000 ft-30,000 ft).

As shown in FIG. 2, by using climb thrust derates CLB1 and CLB2, RoC isreduced at low altitudes, but due to tapering, high altitude RoC is notaffected by climb thrust derate. Particularly, below 10,000 ft, climbthrust derates CLB1 and CLB2 offer better climb performance (e.g.,higher RoC) than a fully rated thrust CLB at MTOW represented by theline 102. Also, above 30,000 ft, climb thrust derates CLB1 and CLB2provide substantially the same RoC as the fully rated thrust CLB at areduce takeoff weight as indicated by the lines 108 and 112 merging withthe line 104.

In examples, using climb thrust derates CLB1 and CLB2 and the differenttapering options may increase the time and distance that the aircrafttakes to reach a desired altitude and may also increase fuelconsumption. For example, when using that maximum climb thrust CLB theaircraft may take about 20 minutes to reach a desired altitude; however,when using CLB2 with a slow tapering option, the aircraft may take 23.5minutes to reach the desired altitude. Using CLB1 and/or other taperingoptions may lead to times that are greater than 20 minutes but less than23.5 minutes.

Also, in an example, when using that maximum climb thrust CLB theaircraft may traverse about 125 nm to reach a desired altitude; however,when using CLB2 with a slow tapering option, the aircraft may fly about145 nm to reach the desired altitude. Using CLB1 and/or other taperingoptions may lead to distances that are greater than 125 nm but less than145 nm. Further, in this example, when using that maximum climb thrustCLB the aircraft may consume about 11300 lb of fuel to reach a desiredaltitude; however, when using CLB2 with a slow tapering options, theaircraft may consume about 12100 lb of fuel to reach the desiredaltitude. Using CLB1 and/or other tapering options may lead to fuelamounts that are greater than 11300 lb of fuel but less than 12100 lb offuel.

Thus, using climb thrust derates CLB1 and CLB2 may lead to an increasethe climb time, distance, and in fuel consumption to reach a desiredaltitude. However, the cruise distance is reduced, and therefore lesscruise fuel is used and the increase in time for the overall mission ortrip is minimal.

FIG. 3 illustrates effect of using climb thrust derates CLB1 and CLB2 onoverall mission of an aircraft 114, in accordance with an exampleimplementation. As depicted in FIG. 3, the mission distance, fuel, andtime are represented by line 116. The mission distance is fixed, whereasthe mission fuel and time may vary.

Line 118 represents climb profile of the aircraft 114 while usingmaximum climb thrust CLB, line 120 represents climb profile of theaircraft 114 while using climb thrust derate CLB1, and line 122represents climb profile of the aircraft 114 while using climb thrustderate CLB2. Lengths of the lines 118, 120, and 122 represent distancetraversed by the aircraft 114 to reach a desired altitude at point 124,whereas projection of the lines 118, 120, and 122 on the line 116represented time taken by the aircraft 114 to reach the desired altitudewhen a respective climb profile and climb thrust level is used.

Cruising distance and time from reaching the desired altitude andbeginning descent at point 126 is represented by arrows 128, 130, and132. Specifically, the arrow 128 represents cruise distance and timewhen using maximum climb thrust CLB, the arrow 130 represents cruisedistance and time when using climb thrust derate CLB1, and the arrow 132represents cruise distance and time when using climb thrust derate CLB2.

As shown by a comparison of lengths of the lines 118, 120, and 122,using CLB2 leads to an increase in distance and time to reach the point124 compared to using CLB1 or CLB. However, as shown by a comparison oflengths of the arrows 128, 130, and 132, using CLB2 leads to a decreasein the cruising distance and time taken by the aircraft 114 to begin itsdescent at the point 126 compared to using CLB1 or CLB. As such, fueland time used while cruising is less for CLB2 compared to CLB1 and isless for CLB1 compared to CLB.

Thus, in examples, when accounting for the fuel and time that theaircraft 114 spends at cruising altitude (after reaching the point 124),the overall fuel and time differences may be small. As an example forillustration, the difference in time may be on the order of minutes andcould be less than a minute, whereas the difference in fuel may be lessthan 150 lb and the difference in fuel cost may be less than $30.

As indicated by these numbers, the differences for the overall missionare small. However, using derated climb thrusts may lead a reduction inTurbine Gas Temperature (TGT) of the engine and a reduction in timespent at TGT. Reduced TGT and reduction in the time-at-TGT (the durationof time that the engine operates at TGT) may reduce engine damage andextend engine life. Thus, the benefit to the engine life and reductionin maintenance cost over the life of the engine may be sufficientlylarge to justify using derated climb thrusts (e.g., CLB1 and CLB2).

FIG. 4 illustrates a block diagram 134 depicting operations associatedwith determining a climb profile of an aircraft, in accordance with anexample implementation. The block diagram 134 is divided into fivecolumns 136A, 136B, 136C, 136D, and 136E, where each column represent aphase during which blocks included in the column could be executed,performed, or implemented.

Specifically, the column 136A is associated with operations that couldtake place during airplane and engine design. The column 136B isassociated with operations that could be performed and parameters thatcould be selected by an airline to be implemented as a default for afleet of aircraft, for example. The column 136C is associated withinformation that could be input by a crew of an aircraft or a dispatchdepartment of airline prior to the flight. The column 136D is associatedwith preflight operations and calculations that could be performed by aflight management computer (FMC) 138 of the aircraft. The column 136E isassociated with preflight operations performed by the FMC 138 duringflight of the aircraft.

The FMC 138 of the aircraft may be coupled to the aircraft and mayinclude computing devices, processors, data storage, memories, etc., andmay be in communication with various systems and subsystems of theaircraft. For instance, the FMC 138 may be in communication with varioussensors, navigation module, trajectory management module, communicationdevices, guidance module, etc. of the aircraft. The FMC 138 may beconfigured to issue thrust and attitude commands in a closed-loopfeedback control manner to guide the aircraft to accomplish particularflight objectives. An example configuration of the FMC 138 is shown inFIG. 17 and described below with respect to FIG. 17.

The block diagram 134 is further divided by dashed line 139 with blocksabove the dashed line 139 representing operations related to theaircraft, whereas blocks below the dashed line 139 represent operationsrelated to the engine of the aircraft.

At block 140, an aircraft and/or engine manufacturer develop climbrating for the aircraft. At the block 140, the engine performancecharacteristics such as maximum thrust, safe operating temperature forthe various compressor and turbine stages of the engine, fuelconsumption rate, maximum safe takeoff thrust, and maximum safe climbthrust may also be determined. In examples, a turbine of an engine ofthe aircraft may include a set of static guide vanes or nozzle vanesthat accelerates and adds swirl to the fluid and directs it to the nextrow of turbine blades mounted on a turbine rotor. Each row of turbineblades may be referred to as a stage of the turbine. For example, theturbine may include a high pressure turbine stage and a low pressureturbine stage where TGT is measured. As such, in examples, at block 140,the aircraft and/or engine manufacturer may develop the climb rating forthe aircraft based on a safe operating temperature within a particularstage of the turbine stages.

The airline may then determine a balance between fuel cost at block 142and mission time cost at block 144 to select a cost index line at block146. Different cost index lines represent a particular balance or weightgiven to the cost of fuel consumed in a mission against a weight givento the time that the aircraft takes to complete the mission. Forinstance, the aircraft can fly at a relatively low speed to save fuel;however, the aircraft would take a long time to reach its destination.Conversely, the aircraft can fly at a relatively high speed to arrive atits destination in a short amount of time; however, fuel cost wouldincrease. Each cost index line represents a particular balance orweights given to fuel cost and mission time. The cost index line is usedby the FMC 138 to determine a climb velocity or airspeed for theaircraft as described below with respect to FIG. 5.

On the engine side, below the dashed line 139, within the column 136B,at block 148, the airline may select the climb thrust derate taperschedule, e.g., select either quick taper schedule or slow taperschedule. In other words, as described above with respect to FIG. 2, theairline may preconfigure the aircraft and the engine such that theaircraft applies a particular climb thrust taper schedule thatrepresents an altitude range during which the aircraft restoresoperating at maximum climb thrust CLB from operating at a particularclimb thrust derate (CLB1 or CLB2). The climb thrust taper schedulecould be slow (e.g., occurring over an altitude range 10,000 ft to30,000 ft) or quick (e.g., occurring over an altitude range 10,000 ft to12,000 ft) to.

Within the column 136C, above the dashed line 139, at block 150,aircraft crew (e.g., pilot, copilot, or airline dispatch department) mayenter mission specific information to the FMC 138. The mission specificinformation may include, for example, an estimated weight of aircraft atthe top of climb (e.g., upon the aircraft finishing the climb flightphase and reaching cruising altitude). The estimated weight of theaircraft at the top of climb may be based on several factors includingthe number of passengers, the amount of fuel that the aircraft isexpected to carry based on how far the destination of the aircraft is,etc.

On the engine side below the dashed line 139, at block 152 the aircraftcrew may select the climb thrust derate value. For example, the FMC 138may generate a display of a graphical user interface in the cockpitshowing climb thrust derate options such as CLB1 (10% derating) and CLB2(20% derating), and the aircraft crew may select (e.g., via a button ortouching a user-interface item on the graphical user interface) eitherCLB1 or CLB2 or other available options.

Within the column 136D, above the dashed line 139, at block 154 the FMC138 determines desired climb airspeed for the aircraft. Airspeed is thespeed of the aircraft relative to the air. The airspeed could berepresented by indicated airspeed (“IAS”), calibrated airspeed (“CAS”),equivalent airspeed (“EAS”), true airspeed (“TAS”), and densityairspeed.

Indicated airspeed may be read off an airspeed gauge connected to apitot static system. Calibrated airspeed may be indicated airspeedadjusted for pitot system position and installation error. Equivalentairspeed is calibrated airspeed adjusted for compressibility effects.True airspeed is equivalent airspeed adjusted for air density, and isalso the speed of the aircraft through the air in which it is flying. Inexamples, calibrated airspeed may be within a few knots of indicatedairspeed, while equivalent airspeed decreases slightly from calibratedairspeed as aircraft altitude increases or at high speeds. With EASbeing constant, true airspeed increases as aircraft altitude increasesas air density decreases with higher altitude.

The FMC 138 may use inputs from the crew such as the estimated top ofclimb weight of the aircraft (from the block 150) and the airlineselected cost index line (from the block 146) to determine the desiredairspeed for the aircraft. FIG. 5 illustrates determination of a desiredairspeed for the aircraft, in accordance with an example implementation.FIG. 5 illustrates a plot 156 having top of climb weight on the x-axisand desired climb calibrated airspeed on the y-axis. The plot 156further depicts several cost index lines such as lines 158A, 158B, and158C among several other illustrated lines.

Each of the cost index lines represent a tradeoff between fuel cost andmission time (time to destination). For instance, cost index line 158Alabelled “0” gives priority to fuel consumption while not taking intoconsideration mission time. The cost index lines are ascendinglylabelled in increments of “20” up to “320.” For instance, the cost indexline 158B is labelled “20” and the cost index line 158C is labelled“320.” The ascendingly labelled cost index lines shift weight andpriority gradually to mission time, indicated by a higher desiredairspeed, while sacrificing fuel efficiency or fuel cost.

The airline may select the cost index line at the block 146 as describedabove based on preferences and priorities of the airline. For example,the airline may choose the cost index line 158B (labelled “20”). Giventhe input information to the FMC 138 indicating the top of climb weighton the x-axis, the FMC 138 determines the desired airspeed based on theselected cost index line 158B. The desired airspeed may be allowed tovary with altitude as the air density decreases, and thus the desiredairspeed is constrained by the cost index line, the estimated top ofclaim weight of the aircraft, and the altitude of the aircraft. The costindex lines are configured (e.g., the slope of the cost index lines isselected) such that the desired airspeed increases the lift force overthe drag force to obtain enhanced aircraft performance

Referring back to FIG. 4, at block 160, the FMC 138 determines the climbthrust schedule. Specifically, the FMC 138 has or receives informationindicating the maximum climb thrust of the engine (the block 140), theclimb thrust derate taper schedule (the block 148), and the climb thrustderate selection (e.g., CLB1 or CLB2 at the block 152) and accordinglydetermines climb thrust schedule.

As an example, for illustration, assuming the maximum thrust is T_(max)and climb thrust derate is CLB1 (10%), then the initial climb thrustlevel is (T_(max) −0.1 T_(max)), which is equal to 0.9 T_(max). Based onthe taper schedule (e.g., quick or slow taper), the climb thrust levelmay be increased over a particular attitude range. For instance, theclimb thrust level may be increased from 0.9T_(max) to T_(max) over analtitude range of 10,000 ft to 30,000 ft. As such, the climb thrustschedule may, for example, be represented as an equation, a table, or amapping indicating the desired climb thrust level of the engine versusaltitude. This way, as the FMC 138 receives from aircraft altitudesensor information indicating an altitude of the aircraft, the FMC 138accordingly determines the corresponding desired climb thrust levelbased on the climb thrust schedule.

At block 162, the FMC 138 sends a command to control the elevators(control surfaces) of the aircraft to control the pitch angle of theaircraft and maintain the desired airspeed determined at the block 154,and sends a command to control engine throttle to maintain climb thrustlevel according to the climb thrust schedule determined at the block160. For instance, the FMC 138 may be in communication with a guidancemodule and a navigation module of the aircraft. The guidance module mayuse the generated airspeed and thrust commands in addition to position,velocity, and wind measurements for the aircraft received from thenavigation module to generate airspeed and thrust commands. The guidancemodule may then communicate the airspeed and thrust commands to anautomatic flight control system (AFCS), which in turn controls enginethrust and aerodynamic control surfaces of the aircraft in order toachieve the commands of the guidance module. The FMC 138 may implement aclosed-loop feedback control on the airspeed and climb thrust level tomaintain the actual airspeed and climb thrust level within a thresholderror value from the desired airspeed and climb thrust level.

FIG. 6 illustrates forces acting on the aircraft 114, in accordance withan example implementation. As depicted in FIG. 6, weight (W) of theaircraft 114 acts downward at its center of gravity 164, Lift (L) actsperpendicular to a longitudinal plane or fuselage reference plane of theaircraft 114, thrust (T) acts in direction of flight path at an angle θto horizon, and drag (D) acts in a direction opposite to the directionof thrust and flight path. Fuselage reference plane is at an angle αfrom the flight path or an angle (θ+α) from the horizon.

The operations described with respect to the block diagram 134 of FIG. 4entail the FMC 138 constraining the climb thrust level to apredetermined climb thrust schedule (the block 160) and constraining theairspeed based on estimated top of climb aircraft weight, cost indexline, and altitude. However, the RoC of the aircraft 114 isunconstrained and the FMC 138 continually adjusts the flight path angleof climb θ to maintain the desired airspeed and thrust level.

While the implementation shown and described with respect to FIG. 4allows for achieving desired engine thrust level and airspeed, thecruise insertion point could vary. The cruise insertion point is a pointat which the aircraft reaches a desired cruise altitude. The point canbe defined by a distance from a departure point that the aircraft takesto reach the desired cruise altitude or a period of time since departurethat the aircraft takes to reach the desired cruise altitude.

FIG. 7 illustrates a plot 166 of a climb trajectory 167 of an aircraftwhile implementing the operations of FIG. 4, in accordance with anexample implementation. The y-axis indicates altitude of the aircraft inft, whereas the x-axis indicates distance from departure point 168 ortime since leaving the departure point 168.

In examples, the Air Traffic Controller (ATC) sets a desired aircraftcruise insertion point 170 indicated by a particular cruise altitude(e.g., 32,000 ft as depicted in FIG. 7) that the aircraft ascends towithin a predetermined distance or time from the departure airport (thepoint 168). Other factors may also affect the desired aircraft cruiseinsertion point 170 such as aircraft capability, airliner rules, andrules of the airport from which the aircraft is leaving.

The operations described with respect to FIG. 4 might not take intoaccount the desired aircraft cruise insertion point 170. In other words,achieving the desired aircraft cruise insertion point 170 might not beset as an objective that the FMC 138 commands the aircraft to achieve.Rather, as described above, the FMC 138 constrains the climb thrustlevel and the airspeed, and adjusts the RoC of the aircraft to maintainthe climb thrust level and the airspeed. As a result, the aircraft mightreach the desired altitude at an actual aircraft cruise insertion point172 that is different from the desired aircraft cruise insertion point170 as shown in FIG. 7.

In some examples, as depicted in FIG. 7, the actual aircraft cruiseinsertion point 172 may be reached before the desired aircraft cruiseinsertion point 170, e.g., the desired altitude may be reached earlieror in a shorter distance than set by the ATC rules. This case indicatesthat the engines of the aircraft may have been overexerted or that ahigher climb thrust level has been used by the aircraft to reach theactual aircraft cruise insertion point 172, without an economic orperformance benefit as the desired aircraft cruise insertion point 170would have been satisfactory. The FMC 138 could have derated the climbthrust level to reach the desired cruise altitude of 32,000 within thedesired distance or time as set by the desired aircraft cruise insertionpoint 170. Such performance would have been acceptable, while protectingthe engine from a high climb thrust level that indicates a higher enginecore temperature and spending more time at the higher engine coretemperature. Therefore, it may be desirable to take the desired aircraftcruise insertion point 170 into account to improve engine life and itsmaintenance cost over a life of the engine.

Additionally, the implementation of FIG. 4 allows the climb thrust levelto return to a fully rate climb thrust level (CLB) at a particularaltitude rather than adhering to the line 102 shown in FIGS. 1-2.Further enhancements in engine life and reduction in maintenance costcould be achieved by allowing the RoC of the aircraft to adhere to theline 102 shown in FIGS. 1 and 2. As described above, derating the climbthrust (i.e., using CLB1 and CLB2) could be phased out over a particularaltitude range as represented by the lines 106, 108, 110, and 112 inFIG. 2. Such phasing out of derating the climb thrust allows theaircraft to restore operating at maximum climb thrust to reduce the timeand distance that the aircraft take to reach the desired altitude.However, causing the aircraft to adhere closer to the line 102 mayachieve further reduction in TGT and time-at-TGT while achieving thedesired aircraft cruise insertion point 170. Operating according to theline 102 rather than tapering or phasing out climb thrust derating maycause an increase in fuel consumption and time and distance to reach thedesired altitude; however, any such increase may be outweighed by theincrease in engine life and reduction in engine maintenance cost over alife of the engine.

FIG. 8 illustrates another block diagram 174 depicting operationsassociated with determining a climb profile of an aircraft, inaccordance with an example implementation. Blocks that are commonbetween the block diagram 134 and the block diagram 174 are referred tousing the same reference number. Similar to the block diagram 134, theblock diagram is divided into the five columns 136A, 136B, 136C, 136D,and 136E representing respective phases during which blocks included inthe column could be executed, performed, or implemented.

As shown in FIG. 8, the blocks 148, 152, and 160 associated withselecting or preconfiguring a derating tapering schedule, a specific ordiscrete climb thrust derate, and determining a climb thrust scheduleare not used. However, other blocks 176, 178, 180, and 182 are added toinclude operations that render the FMC 138 flexible in determining andvarying climb thrust level during the climb flight phase of theaircraft.

At block 176 an aircraft and/or engine manufacturer may develop apredetermined aircraft climb trajectory for the aircraft. In someexamples, the predetermined aircraft climb trajectory could also bereferred to as an optimum aircraft climb trajectory for the aircraft.The predetermined aircraft climb trajectory is determined for “default”levels of climb performance. For instance, the predetermined aircraftclimb trajectory could be determined for a default desired performancethat the aircraft takes 180 nm or 30 minutes to reach a particulardesired altitude such as 32,000 ft. The predetermined aircraft climbtrajectory could be determined as a curve or mapping of altitude versusground distance or altitude versus time.

Developing the predetermined aircraft climb trajectory may take intoaccount several factors such as airframe and engine performancecharacteristics. For instance, developing the predetermined aircraftclimb trajectory takes into consideration characteristics of the engineof the aircraft being designed to minimize undesirable variations inengine severity during the climb flight phase. Particularly, thepredetermined aircraft climb trajectory may be determined to reduce agiven temperature within the engine such as TGT or the temperature atany other turbine stage.

Rather than the airline preconfiguring the aircraft with a climb thrustderate taper schedule (the block 148 in FIG. 4) and the flight crewselecting a discrete climb thrust derate (the block 152 in FIG. 4), atblock 178 in FIG. 8 the aircraft crew may enter information defining orindicating the desired aircraft cruise insertion point. For instance,the aircraft crew may enter a desired altitude to be reached within apredetermined distance or time period from departure.

As such, the FMC 138 has information indicating the predeterminedaircraft climb trajectory (from the block 176) and informationindicating the desired aircraft cruise insertion point (from the block178). Based on this information, at block 180 the FMC 138 determines amodified aircraft climb trajectory for the aircraft. The modifiedaircraft climb trajectory is mission specific as it takes intoconsideration the particular desired aircraft cruise insertion point fora particular flight or tail of a flight.

For example, the FMC 138 may re-scale the predetermined aircraft climbtrajectory determined at the block 176 based on the desired aircraftcruise insertion point to determine the modified (mission-specific)aircraft climb trajectory. The FMC 138 may re-scale the predeterminedaircraft climb trajectory to tailor the climb distance or time to meetthe objective of achieving the desired aircraft cruise insertion point.As such, the predetermined aircraft climb trajectory may be consideredas a first climb trajectory or an initial climb trajectory that the FMC138 later modifies or adjusts to a second climb trajectory or a desiredclimb trajectory that takes into consideration mission-specificparameters and objectives such as the desired aircraft cruise insertionpoint.

As an example, if the predetermined aircraft climb trajectory isdetermined as a curve having a particular slope or slopes that vary withaltitude or climb distance (e.g., ground distance), the FMC 138 maymodify the climb trajectory by modifying the slope(s). As anotherexample, if the predetermined aircraft climb trajectory is determined asa mapping of altitude versus ground distance or altitude versus time,the FMC 138 may modify the climb trajectory by modifying or scaling themapping. In some examples, however, the FMC 138 may implement thepredetermined aircraft climb trajectory without modification or withoutre-scaling. In other words, in some examples, the FMC 138 might not takethe desired aircraft cruise insertion point into consideration, and maythus use the predetermined aircraft climb trajectory.

At block 182, the FMC 138 sends commands to control the elevators(control surfaces) of the aircraft to control the pitch angle of theaircraft and maintain the desired airspeed determined at the block 154.Also, at the block 182, the FMC 138 sends commands to vary climb thrustlevel of the engine during the climb to maintain the desired or modifiedaircraft climb trajectory and achieve the desired aircraft cruiseinsertion point. As mentioned above, the FMC 138 may be in communicationwith the guidance module and the navigation module of the aircraft. Theguidance module may use the generated airspeed and thrust commands inaddition to position, velocity, and wind measurements for the aircraftreceived from the navigation module to generate airspeed and thrustcommands. The guidance module may then communicate the airspeed andthrust commands to the AFCS, which in turn controls engine thrust andaerodynamic control surfaces of the aircraft in order to achieve thecommands of the guidance module.

As such, the FMC 138 may implement a closed-loop feedback control toadhere to the desired or modified aircraft climb trajectory and achievethe desired aircraft cruise insertion point, rather than implementing aclosed-loop feedback control on the airspeed and climb thrust level.This way, the FMC 138 controls the aircraft such that the actualaircraft cruise insertion point is within a threshold error value fromthe desired aircraft cruise insertion point (e.g., within 1-2% from theground distance or time-since-departure indicated by the desiredaircraft cruise insertion point).

Referring back to FIG. 6, the operations described with respect to theblock diagram 174 in FIG. 8 entail the FMC 138 constraining the RoC to apredetermined rate of climb dictated or defined by the modified aircraftclimb trajectory or constraining the RoC to track the line 102 shown inFIGS. 1 and 2. The FMC 138 may also constrain the airspeed based onestimated top of climb aircraft weight, cost index line, and altitude.However, the climb thrust level of the aircraft 114 is unconstrained andthe FMC 138 is configured to continually adjust the flight path angle ofclimb θ and the climb thrust level (T) to adhere to the modifiedaircraft climb trajectory and achieve the desired aircraft cruiseinsertion point.

Thus, if excess aircraft performance is detected, the FMC 138 wouldreduce the climb thrust. For instance, if the FMC 138 determines thatthe aircraft 114 may reach the cruise altitude earlier, or at aparticular ground distance smaller, than indicated by the desiredaircraft cruise insertion point, the FMC 138 may reduce the climbthrust.

As such, rather than using discrete climb thrust derates (e.g., CLB1 orCLB2) and a tapering schedule, the climb thrust is allowed to becontinually adjusted. Although with this configuration, the climb thrustis allowed to vary continually, the climb thrust does not exceed amaximum rated climb thrust determined by the engine manufacturer. Inother words, the climb thrust is allowed to vary to be less than orequal to a maximum rated climb thrust.

With the configuration of FIG. 8, fuel planning for individual missionsmay be improved. Additionally, due to the ability to reduce climbthrust, engine core temperatures may be reduced by not overexerting theengine or over-achieving the desired aircraft cruise insertion point byarriving earlier than indicated by the desired aircraft cruise insertionpoint. Thus, engine maintenance cost may be reduced and engine life isenhanced.

Further, with the configuration of FIG. 8, variability in the cruiseinsertion point may be removed or reduced. FIG. 9 illustrates a plot 184of a climb trajectory 185 of an aircraft while implementing theoperations of FIG. 8, in accordance with an example implementation.Similar to FIG. 7, the y-axis indicates altitude of the aircraft in ft,whereas the x-axis indicates distance from departure point 168 or timesince leaving the departure point 168.

The operations described with respect to FIG. 8 takes into account thedesired aircraft cruise insertion point 170, and the FMC 138 controlsthe aircraft to achieve the desired aircraft cruise insertion point 170,which may entail reducing climb thrust during the climb flight phase. Assuch, the climb trajectory 185 is more shallow or gradual than the climbtrajectory 167 of FIG. 7, and an actual aircraft cruise insertion point186 substantially coincides with the desired aircraft cruise insertionpoint 170. The term “substantially” is used, for example, to indicatethat the actual aircraft cruise insertion point 186 coincides with thedesired aircraft cruise insertion point 170 or is within a thresholdvalue from the desired aircraft cruise insertion point 170 (e.g., within1-2% from the ground distance or time-since-departure indicated by thedesired aircraft cruise insertion point 170).

Although a first aircraft implementing the operations of FIG. 8 mayarrive at a desired altitude later than a second aircraft implementingthe operations of FIG. 4, the climb thrust of the first aircraft isreduced compared to the second aircraft. As a result, the first aircraftmay have less engine wear, enhanced engine life, and reduced enginemaintenance cost compared to the second aircraft, while achievingdesired performance by meeting the desired aircraft cruise insertionpoint 170.

In examples, further enhancement to engine life can be achieved bytaking into consideration other parameters such as engine coretemperatures and the amount of time that the engine or a particularturbine stage thereof spends operating within a predeterminedtemperature range during the aircraft climb phase. In examples, enginedeterioration could occur most severely when operating within aparticular temperature range. Based on the materials used within theengine, that particular temperature range may cause oxidation,corrosion, or breakdown of thermal barrier coatings. It is thusdesirable to avoid operating within that particular temperature range orminimizing the amount of time the engine spends operating in thatparticular temperature range. Taking these parameters (engine coretemperature and the duration of operation within a particular range oftemperatures) into consideration, the FMC 138 may then allow all threevariables (airspeed, climb thrust, and RoC) to change during the climbflight phase.

FIG. 10 illustrates another block diagram 188 depicting operationsassociated with determining a climb profile of an aircraft, inaccordance with an example implementation. Blocks that are commonbetween the block diagrams 134, 174, and the block diagram 188 arereferred to using the same reference number. Similar to the blockdiagrams 134, 174 the block diagram is divided into the five columns136A, 136B, 136C, 136D, and 136E representing respective phases duringwhich blocks included in the column could be executed, performed, orimplemented.

As shown in FIG. 10, in examples, determining a climb profile for theaircraft might not be based on a predetermined aircraft climb trajectorythat is determined for “default” levels of climb performance asdescribed above with respect to the block 176. Further, rather thandetermining a desired, constrained airspeed based on a cost index lineselected by the airline, in the block diagram 188 the airlineestablishes fuel cost at the block 142, mission time cost at the block144, and establishes engine maintenance cost at block 190 for aparticular aircraft.

As examples, the airline or the aircraft manufacturer may establish fuelcost of the aircraft in dollars per lb of fuel ($/lb). Also, the missiontime cost may be established by the airline in dollars per hour offlight ($/hr). Further, at the block 190, the engine manufacturer or theairline may establish engine maintenance cost as a function of a giventemperature within the engine. That given temperature may, for example,be TGT, the temperature at the high pressure compressor, the temperatureat the high pressure turbine, or any other engine core temperature. Forinstance, the airline or the engine manufacturer may generate a table ora curve that plots maintenance cost over the life of the engine versus aparticular engine temperature (e.g., TGT). Such a table or curverepresents an indirect relationship between the climb thrust and theengine maintenance cost because an increased climb thrust may indicate ahigh engine temperature. Additionally, the engine maintenance cost maybe a function of a duration of time that the engine spends operatingwithin a predetermined temperature range.

Information associated with the fuel cost (the block 142), the missiontime cost (the block 144), and the engine maintenance cost (the block190) are provided to the FMC 138 at block 192. At the block 192, the FMC138 may also receive information from the block 178 indicating thedesired aircraft cruise insertion point and information from the block150 indicating the estimated top of climb weight of the aircraft. Then,at the block 192, the FMC 138 takes into consideration the informationfrom the blocks 142, 144, 19, 178, and 150 and determine, during theclimb flight phase: a desired airspeed, a desired climb thrust, and adesired RoC that reduce the overall cost to the airline, while achievingthe desired aircraft cruise insertion point.

As an example for illustration, at the block 192, the FMC 138 or anyother onboard or off board computing device may implement anoptimization routine based on a multi-objective function expressed as afunction of airspeed, climb thrust, and RoC. For instance, a firstfunction ƒ₁ may express fuel cost as a function of the variables ofairspeed (V), climb thrust (7), and RoC; a second function ƒ₂ mayexpress mission time cost as a function of the variables V, T, and RoC;a third function ƒ₃ may express engine maintenance cost (or apredetermined temperature range at a particular location within theengine or a duration of time that the engine spends operating at thepredetermined temperature range) as a function of the variables V, T,and RoC; and a fourth function ƒ₄ may express an error or discrepancybetween an actual aircraft cruise insertion point and a desired aircraftcruise insertion point as a function of the variables V, T, and RoC.

An optimization problem may thus be set to determine a set of feasiblevalues for V, T, and RoC that minimizes or reduces an multi-objectivefunction that is expressed as a combination of the functions ƒ₁, ƒ₂, ƒ₃,and ƒ₄. The feasible values may be constrained to specific ranges. Forinstance, the airspeed (V) may be constrained to a range of values V_(R)between a minimum and maximum value that takes into consideration enginecharacteristics, air density, and top of climb weight of the aircraft(the block 150). Also, the climb thrust (T) may be constrained to arange of thrust values T_(R) between a minimum that prevents enginestall and a maximum value determined by engine design andcharacteristics. Similarly, the rate of climb (RoC) may be constrainedto a range of RoC values RoC_(R) between a minimum RoC that could be setby the ATC or airport and a maximum feasible RoC value determined byengine and aircraft performance characteristics.

The optimization problem may thus be expressed as a minimization (min)problem subject to (s.t.) constraints on the values of the variables V,T, and RoC. As an example, the optimization problem can be expresses bythe following equation:

min(ƒ₁(V,R,RoC), ƒ₂(V,R,RoC), ƒ₃(V,R,RoC), ƒ₄(V,R,RoC))

s.t. V∈V_(R)

T∈T_(R)

RoC∈RoC_(R)   (1)

Such an optimization (or minimization problem) can be implementedperiodically during the climb flight phase, and can be implementedonboard the aircraft (e.g., by the FMC 138) or off-board the aircraft(e.g., by a ground-based computing device or server in communicationwith the aircraft). As a result of the optimization problem, values forairspeed, climb thrust, and RoC are determined to reduce fuel cost,mission time cost, and engine maintenance cost, while achieving thedesired aircraft cruise insertion point.

This mathematical expression is an example for illustration only andother variations could be implemented. For example, an internaltemperature of the engine (e.g., TGT or the temperature at another stagewithin the turbine of the engine) may be set as a constraint such as TGTmight not be within a predetermined temperature range. Anotherconstraint may comprise precluding the engine from operating within thepredetermined temperature range for a period of time exceeding apredetermined period of time.

As another example, the FMC 138 may continually monitor variation inweight and altitude of the aircraft during the climb flight phase. TheFMC 138 may then determine a modified airspeed for the aircraft based onthe variation, and vary the climb thrust to achieve the modifiedairspeed. Other examples are possible.

At block 194, the FMC 138 sends commands to control the elevators(control surfaces) and the engine to achieve the airspeed, climb thrust,and RoC determined at the block 192. As the block 192 determinesadjustment to any of the variables (the airspeed, climb thrust, andRoC), the adjustments are communicated to the block 194 and the FMC 138provides modified commands to the guidance module of the aircraft. As aresult, the aircraft climbs toward the cruising altitude while adheringto values of the airspeed, climb thrust, and RoC that may reduce fuelcost, mission time cost, and engine maintenance cost, while achievingthe desired aircraft cruise insertion point. With the configuration ofFIG. 8, fuel consumption and mission time may be improved, climb thrustmay be varied to reduce engine core temperatures, and thus reducemaintenance cost, while achieving the desired aircraft cruise insertionpoint.

FIG. 11 is a flowchart of a method 196 for varying climb thrust of anaircraft, in accordance with an example implementation. The method 196could, for example, be performed by the FMC 138. In another example,other computing devices could be used to implement the method 196 incollaboration with the FMC 138. The computing devices could be airborneand coupled to the aircraft or could be ground-based. The method 196could, for example, be associated with performing or implementing theoperations of any or a combination of the block diagrams 134, 174, and188. Further, FIGS. 12-16 are flowcharts of methods for use with themethod 196.

The method 196 may include one or more operations, or actions asillustrated by one or more of blocks 198-218. Although the blocks areillustrated in a sequential order, these blocks may in some instances beperformed in parallel, and/or in a different order than those describedherein. Also, the various blocks may be combined into fewer blocks,divided into additional blocks, and/or removed based upon the desiredimplementation.

In addition, for the method 196 and other processes and operationsdisclosed herein, the flowchart shows operation of one possibleimplementation of present examples. In this regard, each block mayrepresent a module, a segment, or a portion of program code, whichincludes one or more instructions executable by a processor (e.g., aprocessor or microprocessor of the FMC 138) or a controller forimplementing specific logical operations or steps in the process. Theprogram code may be stored on any type of computer readable medium ormemory, for example, such as a storage device including a disk or harddrive. The computer readable medium may include a non-transitorycomputer readable medium or memory, for example, such ascomputer-readable media that stores data for short periods of time likeregister memory, processor cache and Random Access Memory (RAM). Thecomputer readable medium may also include non-transitory media ormemory, such as secondary or persistent long term storage, like readonly memory (ROM), optical or magnetic disks, compact-disc read onlymemory (CD-ROM), for example. The computer readable media may also beany other volatile or non-volatile storage systems. The computerreadable medium may be considered a computer readable storage medium, atangible storage device, or other article of manufacture, for example.In addition, for the method 196 and other processes and operationsdisclosed herein, one or more blocks in FIGS. 11-16 may representcircuitry or digital logic that is arranged to perform the specificlogical operations in the process.

At block 198, the method 196 includes receiving information indicativeof a desired aircraft cruise insertion point comprising achieving adesired cruise altitude for an aircraft within: (i) a predeterminedperiod of time from departure, or (ii) within a predetermined distancefrom departure.

At block 200, the method 196 includes receiving information indicativeof an estimated weight of the aircraft upon the aircraft reaching thedesired cruise altitude.

At block 202, the method 196 includes determining a desired airspeed forthe aircraft based on the information indicative of the estimated weightof the aircraft. The FMC 138 may have access to cost informationindicative of: (i) fuel cost, and (ii) mission cost associated with aduration of the flight of the aircraft, and the FMC 138 may determinethe desired airspeed for the aircraft is further based on the costinformation and the estimate weight of the aircraft.

At block 204, the method 196 includes prior to a flight of the aircraft,determining, based on the desired airspeed and the desired aircraftcruise insertion point, a climb trajectory for the aircraft.

At block 206, the method 196 includes during a climb flight phase of theaircraft, varying climb thrust of an engine of the aircraft to followthe climb trajectory and achieve the desired aircraft cruise insertionpoint.

FIG. 12 is a flowchart of additional operations that may be executed andperformed with the method 196, in accordance with an exampleimplementation. The FMC 138 has access to information indicative of apredetermined aircraft climb trajectory, and at block 208, operationsinclude modifying the predetermined aircraft climb trajectory based onthe information indicative of the desired aircraft cruise insertionpoint to determine a modified aircraft climb trajectory. Varying theclimb thrust of the engine includes varying the climb thrust to followthe modified aircraft climb trajectory and achieve the desired aircraftcruise insertion point.

FIG. 13 is a flowchart of additional operations that may be executed andperformed with the method 196, in accordance with an exampleimplementation. At block 210, operations include, while varying theclimb thrust of the engine during the climb flight phase, maintaining arate of climb of the aircraft by sending a command to an elevator flightcontrol surface of the aircraft to adjust a pitch angle of the aircraftduring the climb flight phase, thereby maintaining the rate of climbwhile the climb thrust is varied.

FIG. 14 is a flowchart of additional operations that may be executed andperformed with the method 196, in accordance with an exampleimplementation. At blocks 212, 214, operations respectively includemonitoring variation in weight and altitude of the aircraft during theclimb flight phase; and determining a modified airspeed for the aircraftbased on the variation, wherein varying the climb thrust comprisesvarying the climb thrust of the engine to achieve the modified airspeed.

FIG. 15 is a flowchart of additional operations that may be executed andperformed with the method 196, in accordance with an exampleimplementation. At block 216, operations include determining atemperature at a particular turbine stage within the engine. Varying theclimb thrust of the engine may include reducing the climb thrust to: (i)preclude the temperature from being within a predetermined temperaturerange, or (ii) preclude the engine from operating within thepredetermined temperature range for a period of time exceeding apredetermined period of time. In an example, the temperature at theparticular turbine stage can be determining via a sensor measurement. Inanother example, the temperature may be determined using a model-basedtemperature prediction that estimates a temperature of an engine turbineusing other parameters such as shaft speed, compressor temperature,etc.).

FIG. 16 is a flowchart of additional operations that may be executed andperformed with the method 196, in accordance with an exampleimplementation. The FMC 138 has access to engine maintenance costinformation indicating maintenance cost associated with operating theengine at a given temperature within a particular turbine stage of theengine. At block 218, operations include, during the climb flight phaseof the aircraft, varying at least one of: (i) airspeed of the aircraft,(ii) the climb thrust of the engine, and (iii) rate of climb of theaircraft based on the cost information (fuel cost and mission cost) andthe engine maintenance cost information.

FIG. 17 is a block diagram of the FMC 138, according to an exampleimplementation. The FMC 138 may be used, for example, to performoperations of the flowcharts shown in FIGS. 11-16 and the block diagrams134, 174, 188 as described herein. The FMC 138 may have processor(s)220, and also a communication interface 222, data storage 224, an outputinterface 226, and a display 228 each connected to a communication bus230. The FMC 138 may also include hardware to enable communicationwithin the FMC 138 and between the FMC 138 and other devices or modules(not shown). The hardware may include transmitters, receivers, andantennas, for example

The communication interface 222 may be a wireless interface and/or oneor more wireline interfaces that allow for both short-rangecommunication and long-range communication to one or more networks or toone or more remote devices. Such wireless interfaces may provide forcommunication under one or more wireless communication protocols,Bluetooth, WiFi (e.g., an institute of electrical and electronicengineers (IEEE) 802.11 protocol), Long-Term Evolution (LTE), cellularcommunications, near-field communication (NFC), and/or other wirelesscommunication protocols. Such wireline interfaces may include anEthernet interface, a Universal Serial Bus (USB) interface, or similarinterface to communicate via a wire, a twisted pair of wires, a coaxialcable, an optical link, a fiber-optic link, or other physical connectionto a wireline network. Thus, the communication interface 222 may beconfigured to receive input data from one or more devices, sensors, ormodules, and may also be configured to send output data to other devicesor modules (e.g., the guidance module, the navigation module, the AFCS,etc.). The communication interface 222 may also include a user-inputdevice, such as a keyboard or mouse, for example

The data storage 224 may include or take the form of one or morecomputer-readable storage media that can be read or accessed by theprocessor(s) 220. The computer-readable storage media can includevolatile and/or non-volatile storage components, such as optical,magnetic, organic or other memory or disc storage, which can beintegrated in whole or in part with the processor(s) 220. The datastorage 224 is considered non-transitory computer readable media. Insome examples, the data storage 224 can be implemented using a singlephysical device (e.g., one optical, magnetic, organic or other memory ordisc storage unit), while in other examples, the data storage 224 can beimplemented using two or more physical devices.

The data storage 224 thus is a non-transitory computer readable storagemedium, and executable instructions 232 are stored thereon. Theexecutable instructions 232 include computer executable code. When theexecutable instructions 232 are executed by the processor(s) 220, theprocessor(s) 220 are caused to perform operations of the FMC 138associated with the flowcharts shown in FIGS. 11-16 and the blockdiagrams 134, 174, 188.

The processor(s) 220 may be a general-purpose processor or a specialpurpose processor (e.g., digital signal processors, application specificintegrated circuits, etc.). The processor(s) 220 may receive inputs fromthe communication interface 222, and process the inputs to generateoutputs that are stored in the data storage 224 and output to thedisplay 228 (e.g., a cockpit display). The processor(s) 220 can beconfigured to execute the executable instructions 232 (e.g.,computer-readable program instructions) that are stored in the datastorage 224 and are executable to provide the functionality of the FMC138 described herein.

The data storage 224 may store the information indicative of thepredetermined aircraft climb trajectory. The data storage 224 may alsostore the information associated with engine maintenance cost, missioncost, fuel cost, cost index lines, etc. Such information may bepredetermined or known, and pre-stored on the FMC 138, or can bedetermined, received, or updated periodically or continually via othercomputing devices or modules.

The output interface 226 outputs information to the display 228 or toother components as well. Thus, the output interface 226 may be similarto the communication interface 222 and can be a wireless interface(e.g., transmitter) or a wired interface as well.

The detailed description above describes various features and operationsof the disclosed systems with reference to the accompanying figures. Theillustrative implementations described herein are not meant to belimiting. Certain aspects of the disclosed systems can be arranged andcombined in a wide variety of different configurations, all of which arecontemplated herein.

Further, unless context suggests otherwise, the features illustrated ineach of the figures may be used in combination with one another. Thus,the figures should be generally viewed as component aspects of one ormore overall implementations, with the understanding that not allillustrated features are necessary for each implementation.

Additionally, any enumeration of elements, blocks, or steps in thisspecification or the claims is for purposes of clarity. Thus, suchenumeration should not be interpreted to require or imply that theseelements, blocks, or steps adhere to a particular arrangement or arecarried out in a particular order.

Further, devices or systems may be used or configured to performfunctions presented in the figures. In some instances, components of thedevices and/or systems may be configured to perform the functions suchthat the components are actually configured and structured (withhardware and/or software) to enable such performance. In other examples,components of the devices and/or systems may be arranged to be adaptedto, capable of, or suited for performing the functions, such as whenoperated in a specific manner.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to skill in theart, may occur in amounts that do not preclude the effect thecharacteristic was intended to provide.

The arrangements described herein are for purposes of example only. Assuch, those skilled in the art will appreciate that other arrangementsand other elements (e.g., machines, interfaces, operations, orders, andgroupings of operations, etc.) can be used instead, and some elementsmay be omitted altogether according to the desired results. Further,many of the elements that are described are functional entities that maybe implemented as discrete or distributed components or in conjunctionwith other components, in any suitable combination and location.

While various aspects and implementations have been disclosed herein,other aspects and implementations will be apparent to those skilled inthe art. The various aspects and implementations disclosed herein arefor purposes of illustration and are not intended to be limiting, withthe true scope being indicated by the following claims, along with thefull scope of equivalents to which such claims are entitled. Also, theterminology used herein is for the purpose of describing particularimplementations only, and is not intended to be limiting.

What is claimed is:
 1. A method comprising: receiving, at a flightmanagement computer, information indicative of a desired aircraft cruiseinsertion point comprising achieving a desired cruise altitude for anaircraft within: (i) a predetermined period of time from departure, or(ii) within a predetermined distance from departure; receiving, at theflight management computer, information indicative of an estimatedweight of the aircraft upon the aircraft reaching the desired cruisealtitude; determining, by the flight management computer, a desiredairspeed for the aircraft based on the information indicative of theestimated weight of the aircraft; prior to a flight of the aircraft,determining, by the flight management computer, based on the desiredairspeed and the desired aircraft cruise insertion point, a climbtrajectory for the aircraft; and during a climb flight phase of theaircraft, varying, by the flight management computer, climb thrust of anengine of the aircraft to follow the climb trajectory and achieve thedesired aircraft cruise insertion point.
 2. The method of claim 1,wherein the flight management computer has access to informationindicative of a predetermined aircraft climb trajectory, whereindetermining the climb trajectory comprises: modifying the predeterminedaircraft climb trajectory based on the information indicative of thedesired aircraft cruise insertion point to determine a modified aircraftclimb trajectory, wherein varying the climb thrust of the enginecomprises varying the climb thrust to follow the modified aircraft climbtrajectory and achieve the desired aircraft cruise insertion point. 3.The method of claim 1, further comprising: while varying the climbthrust of the engine during the climb flight phase: maintaining a rateof climb of the aircraft by sending a command to an elevator flightcontrol surface of the aircraft to adjust a pitch angle of the aircraftduring the climb flight phase, thereby maintaining the rate of climbwhile the climb thrust is varied.
 4. The method of claim 1, furthercomprising: monitoring variation in weight and altitude of the aircraftduring the climb flight phase; and determining a modified airspeed forthe aircraft based on the variation, wherein varying the climb thrustcomprises varying the climb thrust of the engine to achieve the modifiedairspeed.
 5. The method of claim 1, further comprising: determining atemperature at a particular turbine stage within the engine, whereinvarying the climb thrust of the engine comprises adjusting the climbthrust to: (i) preclude the temperature from being within apredetermined temperature range, or (ii) preclude the engine fromoperating within the predetermined temperature range for a period oftime exceeding a predetermined period of time.
 6. The method of claim 1,wherein the flight management computer has access to cost informationindicative of: (i) fuel cost, and (ii) mission cost associated with aduration of the flight of the aircraft, wherein determining the desiredairspeed for the aircraft is further based on the cost information. 7.The method of claim 6, wherein the flight management computer has accessto engine maintenance cost information indicating maintenance costassociated with operating the engine at a given temperature within aparticular turbine stage of the engine, the method further comprising:during the climb flight phase of the aircraft, varying at least one of:(i) airspeed of the aircraft, (ii) the climb thrust of the engine, and(iii) rate of climb of the aircraft based on the cost information andthe engine maintenance cost information.
 8. A non-transitory computerreadable medium having stored therein instructions that, in response toexecution by a flight management computer, cause the flight managementcomputer to perform operations comprising: receiving informationindicative of a desired aircraft cruise insertion point comprisingachieving a desired cruise altitude for an aircraft within: (i) apredetermined period of time from departure, or (ii) within apredetermined distance from departure; receiving information indicativeof an estimated weight of the aircraft upon the aircraft reaching thedesired cruise altitude; determining a desired airspeed for the aircraftbased on the information indicative of the estimated weight of theaircraft; prior to a flight of the aircraft, determining, based on thedesired airspeed and the desired aircraft cruise insertion point, aclimb trajectory for the aircraft; and during a climb flight phase ofthe aircraft, varying climb thrust of an engine of the aircraft tofollow the climb trajectory and achieve the desired aircraft cruiseinsertion point.
 9. The non-transitory computer readable medium of claim8, wherein the flight management computer has access to informationindicative of a predetermined aircraft climb trajectory, whereindetermining the climb trajectory comprises: modifying the predeterminedaircraft climb trajectory based on the information indicative of thedesired aircraft cruise insertion point to determine a modified aircraftclimb trajectory, wherein varying the climb thrust of the enginecomprises varying the climb thrust to follow the modified aircraft climbtrajectory and achieve the desired aircraft cruise insertion point. 10.The non-transitory computer readable medium of claim 8, wherein theoperations further comprise: while varying the climb thrust of theengine during the climb flight phase: maintaining a rate of climb of theaircraft by sending a command to an elevator flight control surface ofthe aircraft to adjust a pitch angle of the aircraft during the climbflight phase, thereby maintaining the rate of climb while the climbthrust is varied.
 11. The non-transitory computer readable medium ofclaim 8, wherein the operations further comprise: monitoring variationin weight and altitude of the aircraft during the climb flight phase;and determining a modified airspeed for the aircraft based on thevariation, wherein varying the climb thrust comprises varying the climbthrust of the engine to achieve the modified airspeed.
 12. Thenon-transitory computer readable medium of claim 8, wherein theoperations further comprise: determining a temperature at a particularturbine stage within the engine, wherein varying the climb thrust of theengine comprises adjusting the climb thrust to: (i) preclude thetemperature from being within a predetermined temperature range, or (ii)preclude the engine from operating within the predetermined temperaturerange for a period of time exceeding a predetermined period of time. 13.The non-transitory computer readable medium of claim 8, wherein theflight management computer has access to cost information indicative of:(i) fuel cost, and (ii) mission cost associated with a duration of theflight of the aircraft, wherein determining the desired airspeed for theaircraft is further based on the cost information.
 14. Thenon-transitory computer readable medium of claim 13, wherein the flightmanagement computer has access to engine maintenance cost informationindicating maintenance cost associated with operating the engine at agiven temperature within a particular turbine stage of the engine, andwherein the operations further comprise: during the climb flight phaseof the aircraft, varying at least one of: (i) airspeed of the aircraft,(ii) the climb thrust of the engine, and (iii) rate of climb of theaircraft based on the cost information and the engine maintenance costinformation.
 15. A flight management computer comprising: one or moreprocessors; and data storage storing thereon instructions, that whenexecuted by the one or more processors, cause the flight managementcomputer to perform operations comprising: receiving informationindicative of a desired aircraft cruise insertion point comprisingachieving a desired cruise altitude for an aircraft within: (i) apredetermined period of time from departure, or (ii) within apredetermined distance from departure; receiving information indicativeof an estimated weight of the aircraft upon the aircraft reaching thedesired cruise altitude; determining a desired airspeed for the aircraftbased on the information indicative of the estimated weight of theaircraft; prior to a flight of the aircraft, determining, based on thedesired airspeed and the desired aircraft cruise insertion point, aclimb trajectory for the aircraft; and during a climb flight phase ofthe aircraft, varying climb thrust of an engine of the aircraft tofollow the climb trajectory and achieve the desired aircraft cruiseinsertion point.
 16. The flight management computer of claim 15, whereinthe flight management computer has access to information indicative of apredetermined aircraft climb trajectory, wherein determining the climbtrajectory comprises: modifying the predetermined aircraft climbtrajectory based on the information indicative of the desired aircraftcruise insertion point to determine a modified aircraft climbtrajectory, wherein varying the climb thrust of the engine comprisesvarying the climb thrust to follow the modified aircraft climbtrajectory and achieve the desired aircraft cruise insertion point. 17.The flight management computer of claim 15, wherein the operationsfurther comprise: while varying the climb thrust of the engine duringthe climb flight phase: maintaining a rate of climb of the aircraft bysending a command to an elevator flight control surface of the aircraftto adjust a pitch angle of the aircraft during the climb flight phase,thereby maintaining the rate of climb while the climb thrust is varied.18. The flight management computer of claim 15, wherein the operationsfurther comprise: monitoring variation in weight and altitude of theaircraft during the climb flight phase; and determining a modifiedairspeed for the aircraft based on the variation, wherein varying theclimb thrust of the engine comprises varying the climb thrust to achievethe modified airspeed.
 19. The flight management computer of claim 15,wherein the operations further comprise: determining a temperature at aparticular turbine stage within the engine, wherein varying the climbthrust of the engine comprises adjusting the climb thrust to: (i)preclude the temperature from being within a predetermined temperaturerange, or (ii) preclude the engine from operating within thepredetermined temperature range for a period of time exceeding apredetermined period of time.
 20. The flight management computer ofclaim 15, wherein the flight management computer has access to costinformation indicative of: (i) fuel cost, (ii) mission cost associatedwith a duration of the flight of the aircraft, and (iii) enginemaintenance cost indicating maintenance cost associated with operatingthe engine at a given temperature within a particular turbine stage ofthe engine, and wherein the operations further comprise: during theclimb flight phase of the aircraft, varying at least one of: (i)airspeed of the aircraft, (ii) the climb thrust of the engine, and (iii)rate of climb of the aircraft based on the cost information.